GDR, August 1989: Hanna and Andreas became a target of the secret police and had to give up their plans for their future studies and desired professions. Instead, they face arbitrariness, mistrust and reprisals. Their only chance for a self-determined life lies in fleeing across the Baltic Sea. Fifty kilometres of water separate them from freedom - and only a thin connecting rope around their wrists saves them from absolute loneliness.

After a missed call and a disturbing voicemail from his former colleague Hella Christensen, investigator Simon Kessler sets off for Nordholm. The commissioner is aware that something bad must have happened. When Hella's sailing boat is recovered at sea, traces of her blood and her cell phone are found on it, but there is no trace of the former commissioner herself. A SOKO, headed by the new police commissioner Lena Jansen, takes over the investigation. The investigative team not only has to solve Hella's disappearance, but also the death of 15-year-old Viviane, who was found in the woods by her friend Charlotte Broder and probably died of a drug overdose. Kessler realizes how little he knew about the life of his former colleague. After years, Hella's sister Rieke Lehwald suddenly appears with her husband Paul. Do the two have something to do with Hella's disappearance? Is it about an inheritance or a relationship act?

A missing child causes four families to help each other for answers. What they could not imagine is that this mystery would be connected to innumerable other secrets of the small town.